Attachment fuse plug



May 15, 1934- L. R. MCNAMARA ATTACHMENT FUSE PLUG Filed NOV. 20, 1931 Patented May 15, 1934 UNITED STATES PATENT OFFICE 8 Claims.

My invention relates to what is known as an attachment fuse plug, the same being-adapted for insertion in any outlet for protection of the main fuse related to that outlet.

The fuse plug of my invention is of simple,

compact, and economical construction, and designed to be simply interposed between the conventional attachment plug and the wall socket so that it affords the desired protection for the main fuse without constituting a conspicuous or otherwise objectionable item of the electrical equipment in the home. It is furthermore so constructed that blowing of the fuse link is unattended by any possible iire hazard, and is readily detected by examination of the plug from the outside through a window provided therein for that purpose.

In the drawing, Figure 1 is a view showing my improved plug in side elevation and indicating how the same is adapted to be interposed between an attachment plug and the socket therefor.

Fig. 2 is a face view of the plug.

Figs. 3 and 4 are cross-sections on the correspondingly numbered lines of Fig. 2, and

Fig. 5 is a view of the base portion of the plug,

the cover portion being removed.

In the drawing, wherein the same reference numerals are applied to corresponding parts throughout the views, the attachment fuse plug of my invention is designated generally by the reference numeral 10, and, as appears in Fig. 1, is arranged to be interposed between the conventional attachment'plug 11 of any electrical appliance and the wall socket member, or the correlated wall socket plug l2. That is to say, it is quite common now to provide the equivalent of the plug 12 as the wall socket for reception of the conventional attachment plug like that shown at 11, and the fuse plug of my invention is adapted to be interposed between the plug 11 and the part 12, whether the latter be a separate plug to be threaded in a wall socket or is a permanent wall outlet fixture. The plug 11, like all conventional attachment plugs, has a pair of terminals 13 and 45 14 adapted lnormally for entry in holes 15 and 16 in the plug 12 to make electrical connection with the usual terminal clips provided therein. The fuse plug 10 of my invention is provided with correspondingly spaced terminals 13' and 14 on the base portion 17 thereof for entry in said holes and has holes 15' and 16' in the cap portion 18 thereof Vto receive the terminals 13 and 14, respectively,

so that they will make electrical connection with terminal clips 19 and 20 provided in the base portion 17. Now, the terminal 13 is electrically (Cl. 20o-115.5)

connected with the clip 20 by means of the fuse link 21, and the terminal 14 is electrically connected with the clip 19 by the jumper or bridge piece 22. In that way, it should be clear that when the fuse plug 10 is interposed between the plugs 11 and 12, the fuse link 21 will afford protection for the main fuse provided, of course, that the link 21 is of a size that will blow out at a. lower amperage. This avoids a great deal of annoyance in case an electrical appliance or the extension cord therefor develops a short circuit. Where the attachment plug 11 was inserted directly into the outlet, a short circuit would result in the blowing out of a main fuse and might plunge an entire apartment into darkness. All that is avoided in accordance with my invention and without any additional expense, the plug 10 being replaceable at about the same cost as a main fuse. The fuse plug 10 has the base and cover portion 17 and 18 both molded of hard rubber or any 75 other suitable insulating material. Rivets 23 and 24 are molded in place for the mounting of the terminals 13 and 14', respectively, and similar rivets 25 and 26 are molded in place for the mounting of the clips 19 and 20, respectively. 80 'I'he fuse link 21 is provided with holes at its opposite ends to permit placing the same over the ends of the rivets 23 and 26, which are then upset to complete the assembly and electrically connect the terminal 13 with the clip 20. The 85 bridge piece 22 is likewise provided with holes in the opposite ends thereof to permit placing the same over the ends of the rivets 24 and 25 so that when said rivets are upset, the parts are permanently assembled in place and the terminal 14 is 90 electrically connected with the clip 19. It is obvious that this construction permits of quantity production of the fuses at low cost. The base portion 17 has an annular shoulder 27 formed thereon to permit the annular flange 28 of the cover portion 18 to make a lap joint therewith for fire protection, the parts 17 and 18 being thereby at the same time centered with respect to one another so that a screw 29 can be entered through a hole 30 in the base portion and threaded in a hole 31 in the cover portion to fasten the parts together. The cover portion 18 has a fuse chamber 32 provided therein for accommodation of the narrow portion of the fuse link 21 where the gap will occur when the fuse is blown. A sight opening or window 33 is provided in the cover portion 18 directly over the narrow portion of the fuse, and a disk 34 of glass or other suitable transparent material has a press fit in a counterbore 35 under this opening to seal the chamber 32. An expansion chamber 36 is formed in the cover portion 18 in the diametrically opposite side of the plug, and grooves 37 and 38 formed in the bottom face of the cover portion serve to establish communication between the fuse chamber 32 and the expansion chamber 36. In that way when the fuse is blown, the pressure in the chamber 32 is relieved first of all by allowing equalization of pressure between the chambers 32 and 36. The pressure is furthermore relieved by seepage through a small groove 39 which appears in dotted lines in Fig. 2, opening to the atmosphere by reason of its establishing communication between the expansion chamber 36 and the hole 16'. The groove 39 is, of course, formed in the bottom face of the cover portion 18 like the grooves 37 and 38.

It is believed the foregoing description conveys a good understanding of the objections and advantages of my invention. While I have illustrated and described a fuse plug having terminals to plug into a socket and to have terminals on an attachment plug plugged into it, it should be understood that the invention is not limited to plugs of this particular construction, inasmuch as I have found that it is a simple matter to form a socket on the plug 10 for reception of a screw threaded attachment plug and to provide in place of the terminals 13 and 14' the equivalent screw plug to screw into a wall socket. The appended claims have been drawn so as to cover all legitimate modifications and adaptations.

I claim:

1. A fuse plug of the character described comprising a body of insulating material divided transversely so as to form a base portion and a cover portion, said portions being conformed so as 'to interflt and provide a pressure tight joint therebetween, a fuse chamber and an expansion chamber provided in the cover portion, one or more pressure relief passages alfording communication between said chambers, a fuse element in the fuse chamber, terminal means on the outside of the base portion having electrical connection with said fuse element, and contact means on the inside of the base portion having electrical connection with the fuse element, the cover portion having openings for reception of the terminals of an attachment plug adapted to make detachable connection with the contact means.

2. A fuse plug of the character described comprising a body of insulating material divided transversely so as to form a base portion and a cover portion, said portions being conformed so as to interiit and provide a pressure tight joint therebetween, a fuse chamber and an expansion chamber provided in the cover portion, one or more pressure relief passages affording communication between said chambers, a fuse element in the fuse chamber, terminal means on the outside of the base portion having electrical connection with said fuse element, and contact means on the inside of the base portion having electrical connection with the fuse element, the cover portion having openings for reception of the terminals of an attachment plug adapted to make detachable connection with the contact means, said openings being closed off from communication with the aforesaid chambers.

3. A fuse plug of the character described comprising a body of insulating material divided transversely so as to form a base portion and a cover portion, said portions being conformed so as to interflt and provide a pressure tight joint therebetween, a fuse chamber and an expansion chamber provided in the cover portion, one or more pressure relief passages affording communication between said chambers, a fuse element in the fuse chamber, terminal means on the outside of the base portion having electrical connection with said fuse element, contact means on the inside of the base portion having electrical connection with the fuse element, the cover portion having openings for reception of the terminals of an attachment plug adapted to make detachable connection with the contact means, said cover portion having a sight opening in the wall of the fuse chamber adjacent the fuse element, and a transparent closure for said opening serving to seal said chamber.

4. A fuse of the character described comprising a body of molded insulating material formed in two sections dividing the bodytransversely, the one section being a base portion and the other a cover portion, four rivets suitably molded in place in the base portion in circumferentially spaced relation to one another, a pair of terminals projecting from the base portion having their inner ends attached to and making electrical connection with two diametrically opposed rivets, a pair of terminal clips mounted on the inside of the base portion Yon the remaining two rivets which are likewise disposed in diametrically opposed relation, and a pair of bridge members for electrically connecting the terminals with the respective terminal clips, said members being attached to said rivets, and at least one of said .members being fusible, said cover portion having openings provided therein over said clips for reception of the terminals of an attachment plug to make detachable electrical connection with the clips.

5. A fuse plug of the character described comprising a body of insulating material divided transversely so as to form a base portion and a cover portion, said portions being conformed so as to intert and provide a pressure tight joint therebetween, a fuse chamber and an expansion chamber provided in the cover portion, one or more pressure relief passages aording communication between said chambers, an atmospheric vent for the expansion chamber for relief of pressure in the intercommunicating chambers, a fuse element in the fuse chamber, terminal means on the outside of the base portion having electrical connection with said fuse element, and contact means on the inside of the base portion having electrical connection with the fuse element, the cover portion having openings for reception of the terminals of an attachment plug adapted to make detachable connection with the contact means.

6. A fuse plug of the character described comprising a body of insulating material divided transversely so as to form a-base portion and a cover portion, said portions being conformed so as to interfit and provide a pressure tight joint therebetween, a fuse chamber and an expansion chamber provided in the cover portion, one or more pressure relief passages affording communication between said chambers, a fuse element in the fuse chamber, terminal means on the outside of the base portion having electrical connection with said fuse element, contact means on the inside of the base portion having electrical connection with the fuse element, the cover portion having openings for reception of the terminals of an attachment plug adapted to make detachable connection with the contact means, said opening being closed off from communication with the aforesaid chambers, and an at- 150 mospheric vent for the expansion chamber having communication with one of the last mentioned openings.

"l. A fuse plug of the character described comprising a body of insulating material divided transversely so as to form a base portion and a cover portion, said portions being conformed so as to interflt and provide a pressure tight joint therebetween, a fuse chamber and an expansion chamber provided in the cover portion, one or more pressure relief passages affording communication between said chambers, a fuse element in the fuse chamber, terminal means on the outside of the base portion having electrical connection with said fuse element, contact means on the inside of the base portion having electrical connection with the fuse element, the cover portion having openings for reception of the terminals of an attachment plug adapted to make detachable connection with the contact means, said cover portion having a sight opening in the wall of the fuse chamber adjacent the fuse element, a transparent closure for said opening serving to seal said chamber, and an atmospheric vent for the expansion chamber, whereby to prevent excessive pressure in the fuse chamber active on the transparent closure thereof.

8. A fuse plug of the character described comprising a body of insulating material divided transversely at the middle so as to form a base half portion and a cover half portion, said portions being conformed at their abutting ends so as to interilt and provide a tight joint therebetween, a fuse chamber provided in the cover portion opening from the abutting end thereof, a fuse in the fuse chamber, said cover portion having a sight opening in the other end thereof in the wall of the fuse chamber affording a view of the fuse from outside the plug, terminal means on the outside of the base portion having electrical connection with said fuse element, and contact means on the inside of the base portion having electrical connection with the fuse element, the cover portion having openings for reception of the terminals of an attachment plug adapted to make detachable connection with the contact means.

LEON R. MCNAMARA. 

